1. Field of the Invention:
The present invention relates to a method for inhibiting propagation of virus and to an anti-viral agent. More particularly, the present invention relates to a method for inhibiting propagation of virus wherein a specific oligo- or polydeoxynucleotide is applied to the place infected by virus as well as an anti-viral agent containing a specific oligo- or polydeoxynucleotide.
2. Description of the Prior Art:
At the early stage of the remedy of diseases caused by virus, chemically synthesized medicines and antibiotics were employed as anti-viral agents to inhibit the propagation of virus. In the case of the chemically synthesized medicines, however, their anti-viral spectrum is rather narrow and harmful side-effects brought about by such medicines often come into question. In the case of the antibiotics, on the other hand, there is a detrimental drawback that development of new-type antibiotics are always required in addition to efforts to reduce any harmful side-effect manifested by antibiotics since virus becomes resistant to the antibiotics used and finally becomes immune thereto with the lapse of time.
With the recent development of biotechnology, especially genetic engineering, identification of the structural genes of virus has become a great theme of research among those engaged in the study of microorganisms. In 1977, S. C. Inglis et al. reported the in vitro translation of cytoplasmic RNA extracted from chick embryo fibroblasts infected with influenza A virus in a wheat germ cell-free protein-synthesizing system, with the result that the synthesis of the virus-specific polypeptide corresponding to the hybridized v-RNA segment is reduced [Virology 78, 522-536 (1977)]. However, the experiments referred to in this reference are carried out with a cell-free system having no relation to the study of medicine. Such structural gene identification is also reported by B. M. Paterson et al. in Proc. Natl. Acad. Sci., U.S.A., 74, 4370-4374 (1977). The experiments by Paterson et al. are also carried out with a cell-free system. In these two references, what is used for inhibiting the synthesis of protein is an enormous genetic structure such as RNA itself extracted from the influenza virus in the firstly mentioned reference or rabbit .beta. globin clone P.beta.Gl in the secondly mentioned reference. Such an enormous structure could not be expected to inhibit the intracellular synthesis of protein.
In 1978, P. C. Zamecnik et al. reported that a tridecamer oligodeoxynucleotide complementary to the reiterated 3'- and 5'-terminal nucleotides of Rous sarcoma virus (RSV) is an efficient inhibitor of the synthesis of protein specified by the viral RNA in wheat cell-free system [Proc. Natl. Acad. Sci., U.S.A., 75, 285-288 (1978)] and in an in vitro tissue culture system [ibid. 75, 280-284 (1978)]. Concerning the first reference, the cell-free system is still used as before but some improvement is recognized in respect of using a DNA with a smaller molecular structure for inhibiting the translation of protein. In the second reference, experiments are carried out using the tridecamer in a tissue culture system for inhibiting replication of virus and transformation of cells. The DNA used in these references for inhibiting the replication and the transformation is selected from a region other than a specific coding region and is not desirable. In the same year, N. D. Hastie et al. also reported that hybridization of globin mRNA to its corresponding cDNA was found to specifically inhibit translation of the mRNA in a cell-free system [ibid. 75, 1217-1221 (1978)]. Novel in this reference is only that a certain coding region of DNA is selected for inhibition of the translation by hybridization of mRNA. However, the experiments referred to therein were still carried out in a cell-free system. There has been a demand for developing medicines based on this theory since publication of these references in 1978. Hitherto, however, there has been reported no reference in connection with a device for applying this theory practically to experiments in vivo.
In 1983, a PCT patent application relating to oligonucleotide therapeutic agent and methods of making same (Molecular Biosystems INC., Intl. Publn. No. WO83/01451) was published. However, what is disclosed in this application is a mere statement that (-)-strand DNA selected from a certain coding region inhibited SV 40 transformed cell.
Although the expression "in vivo" is often used in Example 1 of this reference, the descriptions referred to therein are, in view of the context, apparently suggestive of the experiments in vitro cell culture system. Even if such experiments in vitro were deemed as experiments in vivo, they lack concrete conditions thereof and are nothing but a mere mention of expectation of desirable effects. Anyway, this reference suggests for the first time application of RNA-DNA hybridization technique to a medicine but lacks detailed descriptions for substantiating utility as medicines and is nothing more than a mere aggregation of the knowledges manifested at that stage. Thus, what is taught in this patent application involves nothing beyond the technical level disclosed in the references described above.
Under the circumstances mentined above, there is a great demand for providing an entirely new type of anti-viral agent by developing the theory of inhibiting mRNA translation of virus on the basis of the RNA-DNA hybridization technique to realize inhibition of the propagation of virus in vivo.